Cytosolic STs sulfate xenochemicals for detoxification and secretion and also sulfate biological signal molecules such as steroid hormones and bioamines for inactivation and/or storage. Certain sulfated products become carcinogenic. Golgi-membrane STs display high specificity to sulfate distinct sites of polysaccharides. Various glycosyltransferases synthesize polysaccharides and provide STs with substrates. Our research objectives are to eluciadte structure and function of these enzymes. For this, we have used bacterial expression system to produce a large amount of recombinant proteins, have crystallized them, and have solved their 3-dimensional structures. Also Isothermal titration calorimetry is used to investigate various molecular interactactions in solution.